My 2 cents:
Personally, I have had punctures before and I have always had them repaired due to the fact I cannot afford to replace tyres when they haven't done much mileage.
The kind of repair generally dictates what you expect from the rest of that tyres life, ie: externally applied "temporary" roadside repair, 'professional' applied internal repair, etc.
FWIW I have had 2 punctures on my current rear tyre within 2000 miles of each other, and both times I have had it repaired (one was less than 50 miles ago). The first repair has no problems. I have been able to see inside the tyre and see the patch etc to set my own mind at ease and I have faith in these kind of repairs as I can see in my mind how hard it would be for it to acquire a problem and therefor give me a problem.
The repairs were done by a 'professional' place that do many every day, with a large patch that has a length of rubber attached in the middle.. Minimal detail.. Everything is prepped, cleaned, and this length ends up filling the hole in the tyre and the patch is glued down inside the tyre to form an air tight seal and help span any air pressure on the area away from being directly on the rubber filling the hole, alone. Neither the patch nor the attached 'fill' are going anywhere, so I'm fine with this. Recommended speeds are the legal limits and they suggest only 1 repair per tyre before replacement is required.
I have heard of people who regard this repair as perfectly acceptable (I vaguely remember reading one person on this board has 4 of the same repairs in 1 tyre and it's still going strong) and some people discard tyres after acquiring 1 puncture.. As Paul said, pick one. It's your choice, but if you want an honest opinion, I have never had a problem with a 'professional' repair, and would recommend them to people like yourself who cannot justify throwing away a good tyre just yet. :)